Various techniques have been employed to increase the permeability and selectivity of polymeric membranes with regards to gaseous and/or liquid mixtures. U.S. Pat. No. 4,607,088 and its European equivalent 85303088.0 disclose a shaped body having high performance for gas separation, especially for the enrichment of oxygen in air. The shaped body comprises a polymer of a silyl acetylene compound whose surface has been exposed to an atmosphere of low temperature plasma of an inorganic gas. The low temperature plasma is generated by an electrical discharge under conditions which include a frequency in the range from 10 kHz to 100 MHz and a power input of 10 watts to 100 kilowatts.
Japanese patent application Sho 59-62354 discloses a gas separation membrane with high selectivity, composed of an ultraviolet-irradiated body made of a 1-monoalkyldimethylsilylpropyne polymer. The intensity of the irradiation can be any strength 1 mW/cm.sup.2 or higher, with irradiation time varying with irradiation strength. Ultraviolet rays with wavelengths of 40-400 nm are used.
Japanese patent application 60-257807 discloses a gas separation mold comprising a silyl acetylene polymer irradiated by ultraviolet rays of wavelengths between 105 and 200 nm. The irradiation time depends upon the strength and quality of the light source, and the environment of the treatment is specifically stated not to be critical, with one example being air.